Bleach-fixing concentrate

ABSTRACT

A one-part photographic bleach-fixing concentrate containing an iron(III) complex salt, a thiosulphate and a sulphite, a disulphite or a sulphinic acid, remains stable if a phosphate, polyphosphate or polyphosphonate, or a nitrate or bromide is added thereto.

[0001] This invention relates to a one-part bleach-fixing concentrate(BX concentrate) with which bleach-fixing baths can be made up orregenerated, and also relates to a bleach-fixing bath.

[0002] BX baths are used in colour photographic processing in order tooxidise the silver formed by development into a soluble form thereof(bleaching) and in order to dissolve it in this form, together withundeveloped silver halide, by forming a complex from the material to bedissolved (fixing). For these purposes, BX baths contain a series ofnecessary chemicals, namely an iron(III) complex salt as an oxidant, athiosulphate as a fixing agent, and a sulphite, a disulphite or asulphinic acid as a stabiliser for the thiosulphate. These chemicalsexert an effect on each other, so that they cannot be held for anextended period in the same solution. For example, the iron(III) complexsalt oxidises the sulphite, the disulphite or the sulphinic acid. Thethiosulphate is thereby no longer stabilised, so that it thendecomposes.

[0003] For this reason, BX baths are produced as two or three partswhich are not combined with each other until just before they are used.Concentrates which are required for regeneration, i.e. for subsequentaddition to spent chemicals, are likewise produced as two or threeparts.

[0004] Multi-part production of the constituents of a BX tank bath or ofa BX regenerator is disadvantageous, firstly because it is costly anduneconomic, and secondly because it results, time after time, in errorsof addition.

[0005] There is therefore a great need for the chemicals for BX baths tobe produced as one part, and in particular there is a need to provide aone-part BX concentrate which can be converted very easily, namely bydilution with water, to a ready-to-use BX bath, or which can be usedjust as easily for regenerating a BX bath. Attempts to satisfy theseneeds have hitherto failed because of the aforementioned decompositionof the thiosulphate, and also due to insufficient solubility of thethiosulphate, of the sulphite and of the iron(III) complex salt,particularly if the latter is iron(III)-EDTA.

[0006] Surprisingly, it has now been found that these disadvantages canbe overcome if at least one compound from the series comprising aphosphate, polyphosphate or polyphosphonate, or a nitrate or bromide, isadded to the BX concentrate containing the aforementioned constituents.

[0007] Complex salts of Fe(III) which are suitable for photographicbleaching and bleach-fixing batchs are known from numerous documents(e.g. EP 329 088, 584 665, 507 126, 556 782, 532 003, 750 226, 657 777,599 620, 588 289, 723 194, 851 287, 840 168, 871 065, 567 126, 726 203and U.S. Pat. No. 5,670,305).

[0008] The preferred complexing agents for Fe(III) are:ethylenediaminetetraacetic acid (EDTA), propylenediaminetetraacetic acid(PDTA), β-alaninediacetic acid (ADA), diethylenetriaminepentaacetic acid(DTPA), methyliminodiacetic acid (MIDA), ethylenediamine monosuccinate(EDMS), methylglycinediacetic acid (MGDA), ethylenediamine disuccinate(EDDS), particularly (S,S)-EDDS, iminosuccinic acid, iminosuccinicacid-propionic acid, and 2-hydroxypropyliminodiacetic acid.

[0009] Mixtures of complexing agents can also be used.

[0010] Examples of suitable sulphites include ammonium sulphite,ammonium hydrogen sulphite, sodium sulphite, sodium disulphite, sodiumhydrogen sulphite, potassium sulphite, potassium disulphite andpotassium hydrogen sulphite. Examples of suitable sulphinic acidsinclude hydroxymethanesulphinic acid, formamidinesulphinic acid,benzenesulphinic acid, p-toluenesulphinic acid, methanesulphinic acid,o-amido-sulphinic acid and salts thereof.

[0011] Alkali salts and/or ammonium salts can be used as phosphates,e.g. ammonium dihydrogen phosphate, diammonium hydrogen phosphate,triammonium phosphate, potassium dihydrogen phosphate, dipotassiumhydrogen phosphate, tripotassium phosphate, sodium dihydrogen phosphate,disodium hydrogen phosphate, and trisodium phosphate or free phosphoricacid.

[0012] Examples of polyphosphates and polyphosphonates which can be usedinclude sodium hexametaphosphate, sodium tetraphosphate,hydroxyethanediphosphonic acid,N(-2-carboxyethyl)-1-aminoethane-1,1-diphosphonic acid,N,N-bis-(carboxymethylene)-1-aminoethane-1,1-diphosphonic acid,morpholinomethane-diphosphonic acid, nitrilotrismethylene-phosphonicacid, ethylenediamine-tetramethylene phosphonic acid,hexamethylenediaminetetramethylene phosphonic acid,2-phosponobutane-1,2,4-tricarboxylic acid, and2-carboxyethane-phosphonic acid. Free polyphosphoric acids are alsosuitable.

[0013] Alkali and/or ammonium nitrates and bromides can be used asnitrates and bromides.

[0014] The phosphates, polyphosphates and polyphosphonates, nitrates andbromides are preferably added to the concentrate in an amount rangingfrom 0.01 to 2.5 mol/liter, particularly from 0.05 to 1 mol/liter.

[0015] Sodium, potassium and ammonium thiosulphates are particularlysuitable as fixing agents.

[0016] Other constituents can include aminopolycarboxylic acids,rehalogenating agents, acids and alkalies for pH adjustment, bleachingaccelerators, white couplers and buffer substances (see ResearchDisclosure 37 038, February 1995, pages 107 to 109).

[0017] In particular, the pH ranges from 4 to 9.

[0018] In addition, other complexing agents can also be added,individually or in admixture.

[0019] These include:

[0020] polycarboxylic acids: e.g. oxalic acid, malonic acid, glutaricacid, adipic acid, suberic acid, fumaric acid, maleic acid, itaconicacid;

[0021] (poly)hydroxypolycarboxylic acids: e.g. citric acid, glycolicacid, lactic acid, malic acid, tartaric acid, galactaric acid.

[0022] These additional complexing agents are preferably added in anamount from 1 to 200 mmol/l, particularly in an amount from 5 to 50mmol/l concentrate.

[0023] The present invention further relates to a ready-to-usebleach-fixing bath of the type cited at the outset, which ischaracterised in that it additionally contains a phosphate, particularlyin an amount from 0.01 to 0.6 mol/liter, and a polycarboxylic acid or(poly)hydroxypolycarboxylic acid, particularly in an amount from 0.5 to50 mmol/liter.

[0024] The bleach-fixing bath can be produced from the concentrateaccording to the invention if the concentrate contains phosphate and/orpolyphosphate.

EXAMPLES Example 1

[0025] 1 liter of BX concentrate contained ammonium thiosulphatesolution, 57% by weight 400 ml ammonium hydrogen sulphite solution, 66%by weight  80 ml NH₄Fe(III)EDTA solution, 48% by weight 330 ml additivessee below pH 5.5 The pH was adjusted with NH₃ or H₂SO₄.

[0026] The following additions were made to BX concentrates:

[0027] BX 1: no additives

[0028] BX 2: 40 g/l sodium acetate (0.49 mol/liter)

[0029] BX 3: 186 g/l trisodium phosphate dodecahydrate (0.49 mol/liter)

[0030] BX 4: 50 g/l sodium hexametaphosphate (0.082 mol/liter)

[0031] BX 5: 73 ml/l aminotrismethylene-phosphonic acid, concentration50% by weight (0.16 mol/liter) Storage at 60° C. Sodium sulphite content[g/l] Duration of storage BX 1 BX 2 BX 3 BX 4 BX 5 No storage 82.7 82.582.4 82.6 82.3 2 days 55.6 56.0 65.4 64.9 65.1 6 days Precipitates ofsulphur 54.0 54.2 53.8

[0032] The stability of the sulphite was considerably improved by theaddition of phosphate, polyphosphate and polyphosphonate.

[0033] The BX concentrate according to the invention can be used withoutdisadvantages instead of a conventional, two-part BX concentrate, forexample in the standard AP 94 process for the bleach-fixing of exposed,developed colour paper based on chloride-rich silver halide emulsions.

Example 2

[0034] The following additions were made to a BX concentrate as inExample 1 (no additives):

[0035] BX 1: no additives

[0036] BX 2: 40 g/l sodium acetate (0.49 mol/liter)

[0037] BX 3: 48.5 g/l ammonium dihydrogen phosphate (0.49 mol/liter)

[0038] BX 4: 48 g/l ammonium bromide (0.49 mol/liter)

[0039] BX 5: 73 g/l ammonium nitrate (0.49 mol/liter)

[0040] BX 6: 48.5 g/l ammonium dihydrogen phosphate (0.49 mol/l), 20 g/lEDTA acid; 8 g/l citric acid;

[0041] BX 7: 48.5 g/l ammonium dihydrogen phosphate (0.49 mol/l), 16 g/lcitric acid. BX concentrate Formation of crystals after 5 days at −5° C.BX 1 crystals BX 2 crystals BX 3 no crystals BX 4 no crystals BX 5 nocrystals BX 6 no crystals BX 7 no crystals

[0042] The addition of phosphate, bromide or nitrate prevents theformation of crystals in a one-part bleach-fixing concentrate, so that astable concentrate which comprises contents of active ingredients whichwould otherwise not be possible can also be produced.

[0043] The BX concentrate according to the invention is particularlysuitable for short processing times (CD and BX times ranging from 12 to35 seconds) and for a colour developer (CD) which containsdisulphoethylhydroxylamine (HADS) as an antioxidant.

Example 3

[0044] A ready-to-use bleach-fixing bath was produced from the followingcomponents: Ammonium thiosulphate solution, 57% by weight 90 ml sodiumsulphite 10 g NH₄ Fe(III)EDTA solution, 48% by weight 70 ml potassiumdihydrogen phosphate 20 g sodium hexametaphosphate  5 g Made up withwater to 1 liter The pH was adjusted to 6.5 with ammonia or phosphoricacid

[0045] This bleach-fixing bath is distinguished by the improvedstability of the sulphite.

[0046] It can be produced from a concentrate according to the invention.

Example 4

[0047] A ready-to-use bleach-fixing bath was produced from the followingcomponents: Ammonium thiosulphate solution, 57% by weight 90 ml sodiumsulphite 10 g NH₄ Fe(III)EDTA solution, 48% by weight 70 ml potassiumdihydrogen phosphate 20 g EDTA acid  2 g citric acid  1 g Made up withwater to 1 liter The pH was adjusted to 6.5 with ammonia or phosphoricacid

[0048] The bleach-fixing bath is distinguished by the improved stabilityof the sulphite.

[0049] It can be produced from a concentrate according to the invention.

1. A one-part photographic bleach-fixing concentrate containing aniron(III) complex salt, a thiosulphate and a sulphite, a disulphite or asulphinic acid, characterised in that it additionally contains at leastone compound from the series comprising a phosphate, polyphosphate orpolyphosphonate, or a nitrate or bromide.
 2. A one-part bleach-fixingconcentrate according to claim 1, characterised in that its content ofthiosulphate is 0.5 to 5 mol/liter, its content of sulphite is 0.2 to 4mol/liter and its content of Fe(III) complex salt is 0.1 to 1 mol/liter.3. A one-part bleach-fixing concentrate according to claim 1 or 2,characterised in that its pH is 4 to
 9. 4. A one-part bleach-fixingconcentrate according to claim 1 or 2, characterised in that its pH is 4to 6.5.
 5. A one-part bleach-fixing concentrate according to any ofclaims 1 to 4, characterised in that the amount of phosphate,polyphosphate, polyphosphonate, nitrate or bromide is 0.01 to 2.5mol/liter.
 6. A one-part bleach-fixing concentrate according to any ofclaims 1 to 5, characterised in that it additionally contains one ormore complexing agents.
 7. A one part bleach-fixing concentrateaccording to claim 6, characterised in that the additional complexingagent is a polycarboxylic acid or a (poly)hydroxy polycarboxylic acid.8. A one part bleach-fixing concentrate according to claim 6,characterised in that the additional complexing agent is citric acid. 9.A one-part photographic bleach-fixing concentrate containing aniron(III) complex salt, a thiosulphate, and a sulphite, a disulphite ora sulphinic acid, characterised in that it additionally contains aphosphate, polyphosphate or polyphosphonate.
 10. A ready-to-usebleach-fixing bath containing an iron(III) complex salt, a thiosulphate,and a sulphite, a disulphite or a sulphinic acid, characterised in thatit additionally contains a phosphate and a polycarboxylic acid or a(poly)hydroxycarboxylic acid.
 11. A ready-to-use bleach-fixing bathaccording to claim 10, characterised in that the phosphate is containedin an amount from 0.01 to 0.6 mol and the polycarboxylic acid or(poly)hydroxycarboxylic acid is contained in an amount from 0.5 to 50mmol per liter.
 12. A ready-to-use bleach-fixing bath according toclaims 10 and 11, characterised in that it is produced from aconcentrate according to any of claims 1 to 9.